Free-standing superconducting films formed of, e.g., yttrium-barium-copper oxide (YBa.sub.2 Cu.sub.3 O.sub.7-x), have application for optical and infrared detection. For best applications, the superconductive material should be epitaxial since sharp superconducting transitions are needed.
Free-standing superconductive films have been previously prepared by deposition of the selected superconductive material onto a heated carbon substrate. See, e.g., Ng et al., SPIE, Vol. 1477, Superconductivity Applications for Infrared and Microwave Devices II, pg. 15-19 (1991). As carbon is an amorphous material, it was not possible to obtain epitaxial superconductive material in this manner.
Another form of a free-standing superconductive article would be a bulk form such as a microwave cavity or a current-carrying plate that is, e.g., pressed from superconductive powder into the desired shape. Such a bulk form of pressed superconductive material would be suseptible to attack by, e.g., moisture, or suseptible to atmospheric degradation. The protection of such an article by a thin layer of a protective or passivating material would be desirable.
Accordingly, an object of the invention is to provide an essentially substrate-free, free-standing superconductive film including a layer of a template material such as CeO.sub.2 and a layer of an epitaxially oriented superconductive material such as yttrium-barium-copper oxide.
Another object of the invention is to provide a method of preparing such an essentially substrate-free, free-standing epitaxially oriented superconductive film.
Still another object of the invention is a method of protecting a free-standing superconductive article that is, e.g., a bulk form such as a microwave cavity of pressed superconductive material, by coating the superconductive article with a layer of an inorganic protective material such as CeO.sub.2.